1. Field of the Invention
The present invention relates to a worm mechanism and a universal head apparatus using the same.
2. Description of the Related Art
A typical universal head apparatus includes image pickup apparatus and carries out pan and tilt driving using drive force from a motor (i.e., a drive source). Such a universal head apparatus employs a reduction gear in which a worm (i.e., a screw gear) and a worm wheel are used. To make the universal head apparatus move smoothly, removing a backlash between the worm on the drive side and the worm wheel on the driven side is necessary. Then, a technique of urging the worm on the drive side against the worm wheel on the driven side by means of an elastic body is used widely to remove a backlash between the worm and the worm wheel.
Japanese Patent Laid-Open No. 2013-129417 discloses a method for urging a worm shaft toward an axial direction of a worm wheel using an urging member while elastically supporting the worm shaft in the direction of the worm wheel. Japanese Patent Laid-Open No. 2008-100640 discloses a technique of forming a worm integrally with an output shaft of a motor and arranging bearings with the motor and the worm disposed therebetween.
In the related art disclosed in Japanese Patent Laid-Open No. 2013-129417, the worm shaft is tilted about a joint, as a support point, that joins a motor shaft (i.e., a driving shaft) and the worm shaft. When the worm shaft is tilted in such a configuration, coaxiality between a worm shaft and the motor shaft decreases and, as a result, smooth driving becomes impossible. Additionally, in such a configuration, urging an outer part of one of the bearings applies unfavorably large load on the bearing.
In the related art disclosed in Japanese Patent Laid-Open No. 2008-100640, durability decreases although a decrease in coaxiality may be reduced. The reason of the decrease in durability is that excessively large load is applied to a bearing because one of the bearings itself is urged as in the case of Japanese Patent Laid-Open No. 2013-129417.
The present invention provides a worm mechanism with reduced load on bearings and improved durability while reducing a backlash between gears, and also provides a universal head apparatus using the worm mechanism.